[PATCH] mmc: sdhci-of-at91: disable selectively clocks on pm runtime

[Aubin Constans <aubin.constans@microchip.com>]

From: Claudiu Beznea <claudiu.beznea@tuxon.dev>

SAMA7G5's SDMMC run-time clock disabling is not supported.
Add support to avoid this scenario for SAMA7G5.

[Amended with a fix from Romain Sioen below this line]

Sama7 boards are impacted by an unbalanced prepare/unprepare
and enable/disable clock management in sdhci driver due to
the lack of support for SDMMC clock runtime disabling,
managed instead by the PMC driver.

Add conditions in the preset function to manage clock
depending on if the board support runtime clock disabling
and if we come from the probing or restoring procedure.

Add boolean start_clks variable to manage condition
in preset function.

Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Co-developed-by: Romain Sioen <romain.sioen@microchip.com>
Signed-off-by: Romain Sioen <romain.sioen@microchip.com>
Signed-off-by: Aubin Constans <aubin.constans@microchip.com>
---
 drivers/mmc/host/sdhci-of-at91.c | 36 ++++++++++++++++++++++++--------
 1 file changed, 27 insertions(+), 9 deletions(-)

diff --git a/drivers/mmc/host/sdhci-of-at91.c b/drivers/mmc/host/sdhci-of-at91.c
index 7c4ac65f247d..399856643e57 100644
--- a/drivers/mmc/host/sdhci-of-at91.c
+++ b/drivers/mmc/host/sdhci-of-at91.c
@@ -39,6 +39,7 @@ struct sdhci_at91_soc_data {
 	const struct sdhci_pltfm_data *pdata;
 	bool baseclk_is_generated_internally;
 	unsigned int divider_for_baseclk;
+	bool pm_runtime_disable_clks;
 };
 
 struct sdhci_at91_priv {
@@ -149,12 +150,14 @@ static const struct sdhci_pltfm_data sdhci_sama5d2_pdata = {
 static const struct sdhci_at91_soc_data soc_data_sama5d2 = {
 	.pdata = &sdhci_sama5d2_pdata,
 	.baseclk_is_generated_internally = false,
+	.pm_runtime_disable_clks = true,
 };
 
 static const struct sdhci_at91_soc_data soc_data_sam9x60 = {
 	.pdata = &sdhci_sama5d2_pdata,
 	.baseclk_is_generated_internally = true,
 	.divider_for_baseclk = 2,
+	.pm_runtime_disable_clks = true,
 };
 
 static const struct of_device_id sdhci_at91_dt_match[] = {
@@ -164,7 +167,7 @@ static const struct of_device_id sdhci_at91_dt_match[] = {
 };
 MODULE_DEVICE_TABLE(of, sdhci_at91_dt_match);
 
-static int sdhci_at91_set_clks_presets(struct device *dev)
+static int sdhci_at91_set_clks_presets(struct device *dev, bool start_clks)
 {
 	struct sdhci_host *host = dev_get_drvdata(dev);
 	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
@@ -174,7 +177,14 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
 	unsigned int			gck_rate, clk_base_rate;
 	unsigned int			preset_div;
 
-	clk_prepare_enable(priv->hclock);
+	/*
+	 * Manage clock prepare/enable procedure depending on if the board
+	 * support runtime clock disabling and if we come from the probing
+	 * or restoring procedure (for backup+self refresh).
+	 */
+	if (start_clks)
+		clk_prepare_enable(priv->hclock);
+
 	caps0 = readl(host->ioaddr + SDHCI_CAPABILITIES);
 	caps1 = readl(host->ioaddr + SDHCI_CAPABILITIES_1);
 
@@ -223,8 +233,11 @@ static int sdhci_at91_set_clks_presets(struct device *dev)
 	writew(SDHCI_AT91_PRESET_COMMON_CONF | preset_div,
 	       host->ioaddr + SDHCI_PRESET_FOR_DDR50);
 
-	clk_prepare_enable(priv->mainck);
-	clk_prepare_enable(priv->gck);
+	/* Same clock management as for hclock */
+	if (start_clks) {
+		clk_prepare_enable(priv->mainck);
+		clk_prepare_enable(priv->gck);
+	}
 
 	return 0;
 }
@@ -254,9 +267,11 @@ static int sdhci_at91_runtime_suspend(struct device *dev)
 	if (host->tuning_mode != SDHCI_TUNING_MODE_3)
 		mmc_retune_needed(host->mmc);
 
-	clk_disable_unprepare(priv->gck);
-	clk_disable_unprepare(priv->hclock);
-	clk_disable_unprepare(priv->mainck);
+	if (priv->soc_data->pm_runtime_disable_clks) {
+		clk_disable_unprepare(priv->gck);
+		clk_disable_unprepare(priv->hclock);
+		clk_disable_unprepare(priv->mainck);
+	}
 
 	return 0;
 }
@@ -269,7 +284,7 @@ static int sdhci_at91_runtime_resume(struct device *dev)
 	int ret;
 
 	if (priv->restore_needed) {
-		ret = sdhci_at91_set_clks_presets(dev);
+		ret = sdhci_at91_set_clks_presets(dev, priv->soc_data->pm_runtime_disable_clks);
 		if (ret)
 			return ret;
 
@@ -277,6 +292,9 @@ static int sdhci_at91_runtime_resume(struct device *dev)
 		goto out;
 	}
 
+	if (!priv->soc_data->pm_runtime_disable_clks)
+		goto out;
+
 	ret = clk_prepare_enable(priv->mainck);
 	if (ret) {
 		dev_err(dev, "can't enable mainck\n");
@@ -344,7 +362,7 @@ static int sdhci_at91_probe(struct platform_device *pdev)
 		return dev_err_probe(&pdev->dev, PTR_ERR(priv->gck),
 				     "failed to get multclk\n");
 
-	ret = sdhci_at91_set_clks_presets(&pdev->dev);
+	ret = sdhci_at91_set_clks_presets(&pdev->dev, true);
 	if (ret)
 		return ret;
 
-- 
2.43.0